In the medical and surgical fields, it is sometimes necessary to perform procedures to reattach soft tissue to bone. Soft tissue, such as a tendon or ligament, may rupture, become damaged, or detach from a patient's bone as a result of injury or a medical procedure. One common type of such injury is a torn rotator cuff. Surgical treatment of a torn rotator is designed to reattach the damaged tendon(s) back to the humeral head (ball of the shoulder joint) from where it is torn.
Bone anchors are one medical implant than can be used to attach soft-tissue to the bone. These anchors are designed to hold the tissue onto the bone at its point of reattachment to allow the tissue to heal and naturally reattach itself to the bone. Typically, the anchor is implanted into a bore or tunnel predrilled into a bone mass and the tendon or ligament is reconnected to the bone with a suture that is attached to the anchor. With advances in arthroscopic surgery, the use of suture anchors has become more popular because of the ease and speed of their use and because of the decreased surgical exposure and morbidity.
Various types of bone anchors are known in the art. For Example, U.S. Pat. No. 5,645,589 to Li teaches a bone anchor having two sections, each having a group of fingers which interdigitate with the fingers of the other section at the midsection of the device. In operation, the sections are inserted into a bone bore and are pressed together, causing the fingers of one or both of the sections to cross and fan outwards and press into the surrounding bone.
U.S. Pat. No. 5,643,321 to McDevitt teaches a bone anchor comprising an expandable sleeve having at least one slit at one end thereof and an expansion member, i.e. rivet, screw, or nut. In operation, the expansion member is forced into the sleeve causing the slits to open and at least one portion of the sleeve to expand and press into the bone hole. Because the slits are only at one end of the sleeve, the sleeve only expands at one end inside the bone hole.
While advancements have been made to bone anchors since their development, these anchors can be tedious to implant and are still prone to dislodgement. Pullout of the anchor commonly causes the tendon or ligament to retear and, while less common, can cause damage to the surrounding bone. Thus, it is desirable to have a bone anchor that can be easily implanted, yet is firmly lodged within the bone hole to resist pull-out.